JPH0263059A - Formation of minute pattern - Google Patents

Abstract

PURPOSE:To form an opening hole smaller than a 1st resist film and to form a minute resist pattern efficiently by laminating and adhering the 1st resist film and a 2nd resist film different in composition on the flank of the opening hole of the 1st resist film, and removing the nonreacting layer of the 2nd resist film. CONSTITUTION:The 1st resist film 11 is formed on a semiconductor substrate 101 and irradiated with an electron beam 13 as shown by an arrow according to a specific pattern. Then the 1st resist film 11 is developed by a liquid developer to form the opening hole 11a. Then a resist film 12 is formed by coating and a heat treatment is carried out to form a reacting layer 14 of both resist films which is not peeled by the peeling processing of the 2nd resist film 12 at the border between the 1st resist film 11 and 2nd resist film 12. Then, ultraviolet rays are projected so as to peel the 2nd resist film 12 which does not react and then the substrate is dipped in the liquid developer to form the resist pattern. Consequently, the opening hole of the 1st resist film can be set wider than finally needed opening hole size and the fine pattern is easily formed with good reproducibility.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for forming fine patterns, and particularly to integrated circuits,
The present invention relates to a method for forming fine patterns in the manufacture of microwave semiconductor devices made of GaAs.

(Prior Art) In recent years, the characteristics of integrated circuits such as high-speed static RAMs and multipliers, and microwave semiconductor elements made of GaAs have been dramatically improved due to advances in microfabrication technology. In particular, in low-noise microwave semiconductor devices represented by high electron mobility transistors, the gate lengths in practical use have reached 0.3 μm or less. Electron beam exposure is widely used as a method for forming such fine patterns.

FIGS. 2(a) to 2(c) are diagrams specifically showing a method of forming a resist pattern on a semiconductor substrate using an electron beam exposure method. First, as shown in FIG. 2(a), an electron beam resist film 102 is formed on a semiconductor substrate 101. Next, as shown in FIG. 2(b), the electron beam resist film 102
An electron beam 103 is irradiated from the direction shown by the arrow. When a positive resist film is used as the electron beam resist film 102, the portion irradiated with the electron beam is removed by development, as shown in FIG.
A resist pattern 112 is formed thereon. by the way,
In order to stably form a resist pattern with good reproducibility using the electron beam exposure method, exposure conditions and resist film development conditions must be precisely controlled, and the resist film 102 must be precisely controlled.
It is necessary to narrow down the diameter of the electron beam incident on the pattern to the required pattern size or less. In particular, when forming a resist pattern of approximately 0.3 μm, it is desirable to narrow down the diameter of the electron beam incident on the resist film to 0.1 μm or less, as electron scattering within the resist or from the semiconductor substrate cannot be ignored. .

Generally, the diameter of an electron beam incident on a resist film and the electron beam current are in a proportional relationship, and the electron beam current and the time required for exposure are in an inversely proportional relationship when resist films of the same sensitivity are used. Therefore, narrowing down the electron beam diameter increases the time required for exposure, leading to a decrease in the number of processing steps within that time.

(Problems to be Solved by the Invention) As mentioned above, according to the conventional technology, the exposure time increases,
The number of processing per hour is reduced and the electron beam diameter is reduced to 0.
．． In order to set the thickness to 1 μm or less, careful maintenance and adjustment of the electron optical system of the electron beam exposure apparatus is required, which poses the problem that the operation rate of the electron beam exposure apparatus is significantly reduced.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a resist pattern forming method that efficiently forms fine resist patterns.

[Structure of the invention]

(Means for Solving the Problems) A fine pattern forming method according to the present invention includes forming a first resist film on a semiconductor substrate and subjecting it to exposure and development to form a pattern having predetermined openings. step, and the first resist film and the side surface of the opening are coated with the first resist film.
A step of stacking and depositing a second resist film having a different composition from the resist film of the first resist film, forming a reaction layer of both resist films at the contact interface between the two resist films, and removing an unreacted layer of the second resist film. and forming apertures smaller than the apertures in the first resist film.

(Function) In the present invention, the openings smaller than the bloom of the first resist film are finally obtained, so the openings provided in the first resist film can be set wider than the predetermined opening size. Therefore, it is possible to form the resist film with a sufficient margin for the diameter of the irradiated electron beam, and moreover, a fine pattern can be easily achieved with good reproducibility without forming holes in the second resist film.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

First, as shown in FIG. 1(a), a first resist film 11 is formed on a semiconductor substrate 101 using, for example, a positive electron beam resist PMMA (polymethyl methacrylate).
is formed to have a thickness of 1 μm, and then the first resist film 11 is formed to have a thickness of 1 μm.
The electron beam 13 is irradiated according to a predetermined pattern from the direction indicated by the arrow. Next, as shown in FIG. 1(b), the first resist film 11 is developed using, for example, a developer consisting of a mixture of MIBK (methyl isobutyl ketone) and IPA (isopropyl alcohol) at a volume ratio of 1:2. Then, for example, an opening 11a of 0.5 μm is formed. When electron beam exposure is used, a pattern with an opening size of about 0.5 μm can be formed with a relatively large beam current, so the time required for drawing can be shortened.

As the resist film 12, for example, a positive type photoresist AZ1350 (trade name, manufactured by Sibley Co., Ltd.) is used with a thickness of 0.5μ.
The second resist film 12 is peeled off at the boundary between the first resist film 11 and the second resist film 12 as shown in FIG. A reaction layer 14 of both resist films that is not peeled off during processing is formed. Here, the heat treatment after applying the second resist film 12 is performed for the purpose of stably forming the reaction layer 14 of both resist films.

This is not necessarily necessary, since the reaction M14 of both resist films can be formed by simply applying the second resist film 12. Next, in order to peel off the unreacted second resist film 12, the semiconductor substrate is irradiated with ultraviolet rays, for example, and then immersed in an AZ developer to form a resist pattern 15 shown in FIG. 1(d).

The thickness of the resist film on the semiconductor substrate (1) after peeling off the unreacted second resist film 12 is 0.0 mm thicker than the original thickness of the first resist film 12 due to the presence of the reaction layer 14 that is not peeled off. 1μm thicker, and at the same time the area around the opening is 0.1μm thicker.
It is known that the width becomes narrower by μm.

Therefore, if the dimension of the opening 11a in the first resist film is set to 0.5 μm as in the above embodiment, the dimension of the opening 23 after peeling off the second resist film 12 is 0.3 μm.

In the above example, an example was explained in which AZ1350 was used for PMMA, but AZ1350 was used for PMTP, although the dimensions of the openings after peeling off the second resist film 12 were slightly different.
1350 may be combined with a resist such as PMMA II PR-1182 (trade name, manufactured by GAF). Furthermore, the exposure means used to pattern the first and second resist films 11 and 12 is not limited to electron beam exposure, but may be Xa exposure or a combination thereof.

Furthermore, SiO□ or AQ is formed on the semiconductor substrate 101.
It is also applicable to cases where a film of

〔Effect of the invention〕

As described above, according to the present invention, it is possible to set the openings in the first resist film to be wider than the final required opening size, so that the openings in the first resist film can be set to be larger than the diameter of the electron beam to be irradiated. Formation of fine patterns with an opening size of about 0.3 μm or less because it can be formed with sufficient margin and the required openings can be formed simply by applying and peeling off the second resist film. This has remarkable effects that can be achieved easily and with good reproducibility.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are sectional views showing a fine pattern forming method according to an embodiment of the present invention in the order of steps;
Figures (a) to (c) are all cross-sectional views showing a conventional fine pattern forming method in the order of steps. 11 First resist film 12--Second resist film 13--
---1 Electron beam 14--11-----Reaction layer 15 Resist pattern 101--1 Semiconductor substrate agent Patent attorney Norihiro Ogott: :lA +L cyst film I32'fL ) beam 23: open hole No. 1 1! 11: L dystopia' figure (vsZ) 11α: open) and tot: cow'4f23=¥3-roz:<M&b
ynHlZ: L cyst membrane of Kuzu 2 /4:51L et al. 1 1st C (Wakano 1) @2 Fig.

Claims (1)

[Claims] a step of providing a first resist film on a semiconductor substrate and subjecting it to exposure and development to form a pattern having predetermined openings; A step of stacking and depositing a second resist film having a different composition from the resist film of the first resist film, forming a reaction layer of both resist films at the contact interface between the two resist films, and removing an unreacted layer of the second resist film. A method for forming a fine pattern, comprising the step of forming an opening smaller than the opening in the first resist film.